In addition to the buying it directly (as answered below), you can buy futures or other instruments (such as spread bets) that track its price, and these products can be bought from more reputable (and regulated) institutions than Bitcoin exchanges. But as others have said, be aware that this is high risk, and probably not advisable if you don't know much about it.
– John B. LambeOct 17 '18 at 12:17

Meditate on the transience of material wealth until you acquire a mindstate where you are not bothered by losing $1000 to a gamble.

Download, install and run a bitcoin wallet software. Alternatively, use an online wallet service and hope they won't scam you.

Wait until the software synchronized with the blockchain. This can take a while, because it's several GB by now. This is not necessary with an online wallet service because they already did that for their other users.

Use the software/service to create a new wallet (which is just two long codes: Your public wallet address and your secret wallet key).

Create a reliable and secure backup of your wallet key. When you lose it, there is no way to recover your bitcoins. When someone else finds it, they can steal your bitcoins.

Go to the website of a Bitcoin exchange. Pay $1000 in exchange for a bitcoin payment to your wallet address.

Wait until the software says that the transaction arrived in your wallet (can take a while).

Monitor the bitcoin chart until you decide it's time to cash in / rescue what you still can.

Sell your bitcoins to a bitcoin exchange in exchange for real currency (does not need to be the same exchange you bought from)